W EATHER M ODIFICATION A SSOCIATION A NNUAL M EETING
2015
FARGO, N ORTH D AKOTA
A Review of Applications of Acoustic Ice
Nucleus Counters in Weather Modification
Bruce A. Boe, Weather Modification, Inc., Fargo, ND USA
Jack McPartland, Evergreen, CO USA
W EATHER M ODIFICATION A SSOCIATION A NNUAL M EETING
2015
FARGO, N ORTH D AKOTA
The Instrument
• Invented by Gerhard “Gary” Langer (at NCAR)
– “NCAR counter”
– “Langer-banger”
• Operational Principles:
– Sample air is humidified and injected into the top of a cold
cloud chamber with large numbers of CCN, to form a
dense cloud.
– Ice nuclei activate, producing ice crystals, which then
grows as they near the outlet at the base.
– The outflowing air is accelerated sharply as it exits the
chamber. Ice crystals within produce an audible “click”,
which is then converted to a digital signal and counted.
W EATHER M ODIFICATION A SSOCIATION A NNUAL M EETING
2015
FARGO, N ORTH D AKOTA
Cold, Cloudy Chamber
A flashlight placed
atop the Plexiglas
chamber top
illuminates the dense
cloud within.
The silver “line”
visible within is the
thermometer shaft
located about ¾ of the
way down from the
top.
W EATHER M ODIFICATION A SSOCIATION A NNUAL M EETING
2015
FARGO, N ORTH D AKOTA
Variations on a Theme
Snowy Hydro (Australia)
A.B. Super (Unit 3-2)
Not used/pictured: 4th Unit, DRI.
WMI (Formerly Alberta
Research Council)
W EATHER M ODIFICATION A SSOCIATION A NNUAL M EETING
2015
FARGO, N ORTH D AKOTA
Quick History
• Used successfully for decades in ground-based
and airborne applications, summer and winter.
• Because the instrument is not turn-key, there has
at times been some frustrations from persons
trying to use the instrument without complete
knowledge of the operating principles and
nuances as to what to monitor and otherwise pay
close attention to.
• That being noted, the instrument, in the right
hands, has been shown to be very reliable.
W EATHER M ODIFICATION A SSOCIATION A NNUAL M EETING
2015
Functionality
• Over the decades, the AINC
has been reported in the
literature to operate at
specific temperatures,
usually in the
neighborhood of -20°C.
However, these reported
temperatures have
traditionally been those
obtained from
thermometers near the
base of the chamber.
• Actual temperature profiles
in two AINCs, as reported
by Boe et al. 2007 (internal
WMI report), were thus:
FARGO, N ORTH D AKOTA
W EATHER M ODIFICATION A SSOCIATION A NNUAL M EETING
2015
Functionality
• So, though the
temperatures have been
reported as being in the 20°C, the temperature in
much of the chamber is
much warmer.
• Therefore, most AgI IN
activate in the chamber,
but many natural IN do not.
• CONCLUSION: The AINC
does well with AgI, but not
so with natural IN.
• For detecting AgI plumes,
the AINC is highly
effective.
FARGO, N ORTH D AKOTA
W EATHER M ODIFICATION A SSOCIATION A NNUAL M EETING
2015
FARGO, N ORTH D AKOTA
Wx Mod Applications
• Surface Observations
– Fixed locations
– Mobile Van
•
•
•
•
Airborne Observations
Summer – convective applications
Winter – orographic transport and dispersion
Assessment of generator performance
W EATHER M ODIFICATION A SSOCIATION A NNUAL M EETING
2015
FARGO, N ORTH D AKOTA
Generator Performance?
• Place the generator(s) on a vehicle.
• Ignite generator and drive a path
~perpendicular to the wind direction, upwind
of the AINC(s).
• Let the plume pass by the AINC(s).
• Repeat with alternate generator.
• Compare.
W EATHER M ODIFICATION A SSOCIATION A NNUAL M EETING
2015
(Old) Plumage!
• Plumes from
“Skyfire”
generator,
burning AgI-NH4I
seeding solution
burned and
evaluated in CSU
SimLab.
FARGO, N ORTH D AKOTA
W EATHER M ODIFICATION A SSOCIATION A NNUAL M EETING
2015
(New) Plumage!
• Plumes from
WMI “Wyoming”
generator,
burning
“Wyoming”
seeding solution.
FARGO, N ORTH D AKOTA
W EATHER M ODIFICATION A SSOCIATION A NNUAL M EETING
2015
Field Applications
FARGO, N ORTH D AKOTA
W EATHER M ODIFICATION A SSOCIATION A NNUAL M EETING
2015
FARGO, N ORTH D AKOTA
Ground-Based Operation
One of the most
straightforward
applications is the
verification of
targeting.
This trace, from a
Wyoming seeding
event, confirms
transport of a strong
plume from the
ground-based
generators to the
target area.
W EATHER M ODIFICATION A SSOCIATION A NNUAL M EETING
2015
FARGO, N ORTH D AKOTA
Ground-Based Operation
The AINC can also be
used to record the
passages of plumes
from more distant
sources.
In this plot, a
number of plumes
originating from
seeding on a more
distant mountain
range are shown.
W EATHER M ODIFICATION A SSOCIATION A NNUAL M EETING
2015
FARGO, N ORTH D AKOTA
Mobile AINC Detection at the Surface
• When all-weather roadways are available,
AINCs can be operated within a mobile
platform, allowing measurements to be made
at multiple locations. Allows sampling
through plume transects (assuming steadystate conditions).
W EATHER M ODIFICATION A SSOCIATION A NNUAL M EETING
2015
Airborne Operation
Airborne seeding,
upwind of barrier
at approximate
barrier elevation.
Sampling after
seeding by flying
over and
downwind of the
barrier,
perpendicular to
the seeding pass.
(Grand Mesa, CO,
Super and Boe
1988)
FARGO, N ORTH D AKOTA
W EATHER M ODIFICATION A SSOCIATION A NNUAL M EETING
2015
Airborne Operation
Flown downwind
of source(s), often
perpendicular to
prevailing wind.
In this plan view
the wind is from
the WSW.
Most passes flown
just upwind of the
crest line (varying
altitudes).
(Medicine Bow
Range, WY, Boe et
al. 2014).
PLAN VIEW
FARGO, N ORTH D AKOTA
W EATHER M ODIFICATION A SSOCIATION A NNUAL M EETING
2015
FARGO, N ORTH D AKOTA
Airborne Operation
Same as previous slide, but
vertical cross-section.
Intention was to fly moreor-less constant altitude,
but mountain turbulence
had the ultimate say.
(Medicine Bow Range, WY,
Boe et al. 2014)
These data were used to
help validate a numerical
model (Xue et al. 2014).
VERTICAL
XS
W EATHER M ODIFICATION A SSOCIATION A NNUAL M EETING
Airborne Operation
Same as previous slides,
aircraft sampling path shown
projected in pseudo-3D.
Ascent and descent from/to
Cheyenne are included.
2015
FARGO, N ORTH D AKOTA
W EATHER M ODIFICATION A SSOCIATION A NNUAL M EETING
2015
FARGO, N ORTH D AKOTA
Airborne Operation
Same case as previous
three slides, but
measurements from
ground-based AINC sited
near project target area.
Diamonds indicate the
times and concentrations of IN measured
concurrently aloft.
(Medicine Bow Range,
WY, Boe et al. 2014)
SURFACE
AINC OBS
W EATHER M ODIFICATION A SSOCIATION A NNUAL M EETING
2015
FARGO, N ORTH D AKOTA
Limitations
• NOT a turn-key instrument. Must be
monitored throughout data collection by a
knowledgeable technician.
• Doesn’t reliably detect most natural IN.
• Over many hours (~ 8) the chamber may begin
to ice up, producing non-IN-nucleated ice.
When this happens, a shut down to melt off
accumulated ice resets the system.
W EATHER M ODIFICATION A SSOCIATION A NNUAL M EETING
2015
FARGO, N ORTH D AKOTA
Advantages
• Great for detecting AgI.
• Can fly on light aircraft.
• Few alternatives – the CFDC (DeMott, Rogers)
is large and thus –if available – can be flown
only on larger aircraft.
• DMT says their IN counter is not
designed/intended for airborne operation.
W EATHER M ODIFICATION A SSOCIATION A NNUAL M EETING
2015
FARGO, N ORTH D AKOTA
Questions?
Bruce Boe
[email protected]